When a press, e.g. a cutting press, is in use, it is desirable that the operator be able to readily manipulate both the work to be operated on as well as any tools, e.g. cutting dies, and generally to have good visibility over the operating area. In a conventional press, the upper platen, being mounted above the lower platen, reduces such visibility and interferes with such manipulation, unless of course in the rest condition of the press the "daylight" gap between the platens is relatively large.
To overcome this problem, various proposals have been put into practice, e.g. presses in which the upper platen (or beam) swings into and out of opposed relationship with the lower platen about an axis perpendicular to the lower platen, or is capable of moving bodily fore-and-aft of the press into and out of such relationship; such machines are respectively referred to as "swing beam" and "receding head" presses.
Alternatively a so-called "travelling head" press is available wherein a fixed cross-beam is mounted above the lower platen, being of the same, or substantially the same, depth (i.e. dimension fore-and-aft of the press) as the lower platen. The lower platen provides a support for a carriage which is movable widthwise of the lower platen and which in turn supports a hydraulic ram carrying an upper platen. In such a machine, the carriage is supported wholly beneath the cross-beam so that the upper platen always remains in opposed relationship with the lower platen, the arrangement being such that, when pressure is applied by the hydraulic ram, in an operating stroke of the press, bearing surfaces of the carriage are thrust against co-operating surfaces on the cross-beam at both the front and rear thereof.
In general, the "daylight" gap thus provided in travelling head presses is adequate to afford sufficient visibility and allow the operator room to manipulate the work and any tools on the lower platen. It will be appreciated, however, that restrictions are nevertheless imposed by the cross-beam, as compared, for example, with a swing beam press or a receding platen press.